The crust of
the Earth is rock, but as it breaks down into smaller fragments
and particles it evolves into soil, sand, silt and clay. Clays
are the smallest and finest of the mineral particles, and they
are typically made up of silicate crystals that can take the
shape of well-formed hexagonal structures that are the basis of
biological molecules. Such crystals could have served as the
template upon which the biological molecules could form their
similar hexagonal structures. Graham Cairns-Smith of Scotland's
University of Glasgow suggests that clays are
"proto-organisms" that could have served as the
pattern for living systems. He notes that metals in clay
lattices can form complexes with the precursors of proteins and
DNA. These lattices provide the molecular structure that is
necessary to store the energy needed to catalyze chemical
reactions, and most importantly, to reproduce. In a paper titled
"Clay" published in the April 1979 issue of Scientific
American, Georges Millot, who is a member of the French Academy
of Sciences and professor of geology at the Universite Louis
Pasteur in Strasbourg, also confirms the unique electrochemical
properties and geometric structure of clay. Millot believes
these specialized properties may have played an important part
in allowing amino acids to evolve into the long peptide chains
that make up one of the key biological structures: the
proteins.